互耦效应对双散射MIMO系统信道容量影响研究

多入多出(MIMO)传输技术是第四代移动通信系统的关键技术之一,而小尺寸间隔下天线阵元间的互耦效应则是有可能影响MIMO系统性能的一个重要因素。文中首先研究分析了一种接近实际电波传输环境的、收发端皆存在散射体的双散射MIMO信道传输模型,然后将天线互耦效应引入此MIMO传输系统;接下来通过建立多天线系统等效互耦效应网络模型,推导了互耦效应影响下空间相关系数和信道容量表达式;最后通过计算机仿真研究了双散射环境下天线阵元互耦对MIMO系统信道容量的影响。仿真实验表明:双散射环境下,互耦效应将降低MIMO系统信道容量。     

互耦作用对MIMO系统信道容量的影响

简单概括了无线多输入多输出（MIMO）系统及其信道容量,应用矩量法分析了因互耦作用引起的天线阵各阵元辐射图的变化,进而应用已提出的射线追踪模型分析了一个4.4MIMO系统接收端阵元间距不同时互耦作用对信道容量的影响。仿真结果说明在接收端使用多天线,阵元间距不可能太大的情况下,考虑互耦作用后,在小阵元间距（d=0.4λ）时就可得到较大的信道容量。得出结论在接收端阵元间距较小的情况下,互耦是一个有利的因素,在系统分析和设计时可以有效地加以利用。     

考虑互耦的平面相控阵天线波束形成

针对互耦会影响天线方向图的问题,首先用矩量法精确分析了考虑互耦影响时平面相控阵天线阵元的电流分布,仿真实现了阵元互耦对相控阵天线波束形成的影响效果,然后用软件补偿的方法补偿互耦所造成的影响,从而完成了相控阵天线波束形成的综合.     

8～12 GHz Vivaldi槽缝天线阵设计及综合

设计出口径为18 mm的8~12 GHz Vivaldi槽缝天线,并对由此组成的12元线阵进行了互耦研究,讨论了互耦对单元方向图的影响,提出了用本征方向图思路来综合天线阵,结合改进后的遗传算法,对包含互耦的12元Vivaldi线阵的副瓣电平进行了优化。结果表明,相比于传统方法,如切比雪夫综合法,本方法有效地解决了天线阵互耦问题,并对任意布阵的天线阵均适用,有较好的实用价值。     

互耦对微带阵列天线方向特性影向的研究

本文针对微带天线阵元之间的互耦对辐射特性的影响进行研究,以矩形贴片构成的四单元直线阵为研究平台,导出相应的计算公式,基于时域有限差分法建立天线模型,进行仿真测试,讨论了在不同位置对阵元馈电的情况下,互耦对阵列方向图的影响,为在互耦状态下微带天线阵的设计提供了参考.     

阵元间互耦对测向性能的影响与分析

用矩量法严格分析了考虑互耦影响下，常用于超分辨测向的各种天线阵阵元的电流分布。然后根据等效网络法，分析了各种常见的天线阵阵元间的互耦以及互耦对一维和二维测向性能的影响，并为实际的天线阵布阵提供了一些技术参考。     

互耦影响下的自适应圆阵分析

本文用矩量法严格分析了考虑互耦影响时自适应天线阵元的电流分布，给出了计算电流的解析式，并计算了八单元圆阵的电流分布。用等效网络法推导了考虑互耦影响时的最佳权矢量。仿真计算了不同阵元间距时，自适应阵的数字波束赋形。     

对数周期偶极子天线阵的互耦分析

结合1970年Robert H. Kyle提出的对数周期天线间互耦的分析方法和1973年Hyong K Choe、Charles E Smith提出的对数周期天线分析方法分析了对数周期偶极子天线组阵时单元间的互耦,给出了阵中单元考虑互耦与不考虑互耦影响的电流分布、阵中方向图以及驻波比,并用该方法和Feco仿真软件计算了天线阵方向图,二者较好的一致性表明了该算法的正确性,得到了互耦对天线性能影响的结论。     

计入阵元间互耦影响的阵列方向性图综合

基于自适应天线理论，在考虑了天线阵中阵元间互耦影响的情况下，对均匀和非均匀直线阵列的方向性图进行了综合，并讨论了加权值幅度和相位误差对天线阵列方向性图的影响。     

空间谱估计测向中通道失配与阵元间互耦的一次性补偿

在空间谱估计测向系统中，各接收通道中的幅相失配和天线阵元间的互耦是导致测向精度和分辨率下降的主要原因。本文分析了这两种因素影响测向系统性能的机制，提出了一种可一次性补偿接收通道的幅相失配和阵元间互耦的有效方案。     

Correlation and capacity of MIMO systems and mutual coupling, radiation efficiency, and diversity gain of their antennas: simulations and measurements in a reverberation chamber

MIMO systems are characterized by their maximum available capacity, which is reduced if there is correlation between the signals on different channels. The correlation is primarily caused by mutual coupling between the elements of the antenna arrays on both the receiving and transmitting sides. Similarly, diversity antennas can be characterized by a diversity gain that also is affected by mutual coupling between the antennas. We explain how such MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes. In the MIMO example under investigation, the mutual coupling reduces both correlation, which increases the capacity, and radiation efficiency, which decreases it, and the combined effect is a net capacity reduction. We also explain how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber. The measurements show good agreement with simulations.     

Mutual coupling in multi-element array antennas and its influence on MIMO channel capacity

The effects of mutual coupling between receive elements in a multi-element antenna on multiple-input multiple-output (MIMO) system capacity are reported. The results are based upon analysis of mutual coupling calculated for a measured linear array of five printed dipole elements with 0.56 of a wavelength spacing. It is shown that the presence of mutual coupling at the receive array antenna leads to additional correlation between spatial channels and results in a loss of MIMO system capacity.     

互耦效应对超大规模MIMO天线系统信道容量的影响

超大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)天线系统是6G的关键技术,由于天线单元间距很小,多个天线单元的互耦效应是影响其性能的因素之一。建立了基于石墨烯基贴片天线阵列-子阵列架构的超大规模MIMO天线系统,推导出了互耦效应影响下的信道容量表达式。通过电磁场数值计算仿真了超大规模MIMO天线系统的信道容量,结果表明,在不考虑互耦效应时,超大规模MIMO天线系统的信道容量与子阵列天线单元数、子阵列数以及发射机功率正相关;在互耦效应的影响下,系统的信道容量降低,互耦效应的强弱与子阵列天线单元的间距有关,天线单元间间距越小,相邻天线间的互耦效应越明显,系统的信道容量越小。该仿真结果可以为6G中超大规模MIMO天线系统的设计提供参考。     

Effect of Signal and Noise Mutual Coupling on MIMO Channel Capacity

In this paper we analyze the impact of mutual coupling on MIMO channel capacity, considering its effect on both signal and thermal noise. We calculate noise correlation matrix in the multi-antenna system with closely spaced antenna by applying Nyquist’s thermal noise theorem. Then, we employ the noise correlation matrix in the channel capacity formula, which enables the identification of thermal noise correlation contribution on the MIMO channel capacity. In addition, we examine the variations in the mean branch signal-to-noise ratios (SNR) due to the noise correlation. Our simulation results corroborate the theoretical analysis that mean and outage MIMO channel capacity is underestimated if noise correlation due to mutual coupling effect is not accounted for.     

Reduction of mutual coupling and cross-polarization of a MIMO/diversity antenna using a string of H-shaped DGS

In this article, a simple string of H-shaped defected ground structure (DGS) is used to reduce the mutual coupling and cross-polarization of a MIMO antenna. A MIMO antenna has been designed using two identical square patches to operate at the frequency of 2.4 GHz. The proposed DGS decreases the direct coupling path among the closely spaced (edge to edge gap 0.038 λ₀) patches and thereby reduces the mutual coupling and cross-polarization by 46 dB and 11 dB respectively. To study the amount of mutual coupling is decoupled; a new term namely, coupling to decoupling ratio (CDR) has been defined. A mathematical model is developed using multiple polynomial regression analysis techniques to observe the dependency of CDR as a function of frequency and inter-element spacing. Also, an equivalent circuit of the DGS is constructed and validated. Diversity performance of this MIMO antenna is presented through Envelope Correlation Coefficient (ECC) and Mean Effective Gain (MEG) ratio and well acceptable values of 0.0002 and 0.03 dB are obtained respectively. A prototype is fabricated and measured. The experimental results show good agreement with that of the simulated results. Maximum peak gain of 2dBi and radiation efficiency of 74% also proves the practicality of this design.     

天线匹配对莱斯信道下紧凑MIMO系统性能的影响

深入研究了存在天线互耦和空间相关时,天线匹配网络对莱斯信道下多输入多输出MIMO系统性能的影响,建立了包含相关莱斯信道、天线互耦和匹配网络的(MIMO)系统模型.通过仿真分析了匹配阻抗、天线互耦、空间相关性以及信道衰落环境对包络相关性和信道容量的影响.实验结果表明:莱斯信道下匹配阻抗对MIMO系统的影响与瑞利信道情况下有所不同,适当地选择天线匹配阻抗可以改善MIMO系统的性能.     

室内MIMO无线信道模型和信道容量研究

本文从工程的实际出发,首先提出一种修正的室内MIMO无线信道模型,该模型有效地修正先前室内MIMO无线信道模型的不足,具有明显吻合室内实际通信环境的特点,然后分析天线方向性以及天线单元间的互耦对室内MIMO无线信道容量的影响.数值模拟验证了这种影响,并得到在一定条件下互耦导致的天线方向图畸变产生角度分集,提高信道容量,互耦对空域相关性无影响的条件以及室内丰富的多径使天线方向性对信道容量的影响不明显等结论.最后,实验也证实理论分析.     

A Novel Numerical Model for Simulating Three Dimensional MIMO Channels With Complex Antenna Arrays

We develop a novel three-dimensional (3D) numerical model for rigorously simulating mutual coupling effects on the channel capacity of the multiple input multiple output (MIMO) systems. In this model, the efficient integral equation method mutlilevel Green's function interpolation method (MLGFIM) is for the first time employed to calculate the input admittances and radiation patterns of the transmit and receive antennas of MIMOs. Comparing with the Method of Moments whose complexity is $O(N^{2})$ , MLGFIM has an efficiency of $O(Nlog N)$ and is suitable for efficiently solving antenna arrays problems. To accurately model the EM wave propagation, we 1) use the ray tracing method to obtain the multi-paths and 2) rigorously obtain the dyadic path loss factor model from which a novel stochastic path loss model that is flexible for both the environments with PEC walls and that with infinite thick lossless dielectric walls is devised. Using the proposed model, we successfully analyze mutual coupling effects on the 3D correlation of a 2-by-2 monopole array and the indoor channel capacity of a 20-by-20 planar array and a 20-by-20 icosahedron array. The numerical examples in this paper demonstrate the efficiency of our model for simulating the MIMO system with complex radiators.      

基于天线互耦影响的大规模MIMO TDD系统信道互易性校准算法

射频器件的非理想性和信道的时变特性影响大规模多输入多输出（multiple-input multiple-output，MIMO）系统时分双工（time division duplex，TDD）模式的信道互易性，天线阵列的耦合效应影响信道矩阵的相关性.文中提出一种基于互耦影响的大规模MIMO互易性联合校准算法，将天线之间的互耦效应引入信道矩阵，采用OTA（over-the-air）校准算法和基于自回归（auto-regression，AR）模型预测信道矩阵相结合的方案实现同时校准射频非理想性和信道时变特性引起的互易性损失.仿真结果表明，该算法能够提高系统容量，降低误码率，有效地补偿互易性损失.本文算法可以为大规模MIMO系统的多因素联合校准提供参考.